The polybrominated biphenyls (PBBs) are inducers of hepatic mixed-function oxidases. The purpose of this study is to compare the structure-activity relationships of 2,4,5,2',4',5'-hexabromobiphenyl (2,3,4-HBB), and other components of the commercial polybrominated biphenyl mixture, Firemaster BP-6 as inducers of cytochromes P-450 and P,450 and to relate these effects to hepatic toxicity.